1. Field of the Invention
The present invention relates to a lower inertial compact disc drive, and especially to a disc drive having a small inertia, in that the disc and laser head are retained still. A displacement device alternates the reading and writing positions. Thereby, it is a lower power and lower inertia device.
2. Description of the Related Art
The compact disc drive device is a most frequently used storage medium, which can be approximately divided into three classes: compact disc read only memory (CDROM), CD readable (CDR) and CD readable and writeable (CDRW). In current technology, in reading or writing operation, a CD drive causes that a disc to rotate and the laser head moves reciprocally along a straight path. However, since the inertia of the disc is large, and the laser head and its attachments are heavier and moves reciprocally and frequently, much power is required, the vibration is large and much heat energy is released.
The disc in low speed CD drive moves with a constant linear velocity (CLV). However, the current technology partial constant angular velocity (PCAV) or constant angular velocity (CAV) is used. As the laser head reads or writes data at any position, the motor rotates with a constant speed. To speed the read or write data is to speed the rotation of the motor, this is a conventional way. Currently, some CD drives and DVDROMs use xe2x80x9cTrue X multi-beamxe2x80x9d technology that assures that the read speed is constant in whole disc. It is only alternated responsive to the mass of the CD or the operation system employed.
Current technologies for reading data on DVD are not consistent. In the past, to be compatible with CDROMs, DVDROMs, two lasers heads for dual-reading is used. Currently a single lens technology is used. Besides, the digital servo system can be used to realize the automatic adjustment of a CD drive so as to increase the preciseness of reading data. Dual dynamic shock-proof system (DDSS) may be used to reduce the vibration of a compact disc in high speed. Auto balance system (ABS) can be used to retain the compact disc in a horizontal condition so that the reading ability of the CD is increased greatly. Automatic intellectual error correction (AIEC) may greatly increase the amount of data read by the compact disc. By above novel technologies, the performance of compact disc drive is improved. However, in current compact disc drives, the disc rotates with a high speed and the laser head moves reciprocally along a straight path. Since the compact disc has a large inertia and the laser head is heavier, the current CD drive needs a larger power and a large vibration and consumes much power. Thereby, the use of the current CD drive is limited and cannot be used in a personal digital assistant (PDA). PDAs have the functions of calculators, phones, facsimile machines, and networks. These functions are realized wirelessly. The peripherals of PDAs needs low power without much power being released. However, the current CD drive cannot match these requirements due to the large inertia of the disc and the heavier laser head.
Accordingly, the primary object of the present invention is to provide a lower inertial compact disc drive, wherein the disc and laser head are motionless. The laser beam for writing and reading data is transferred by optic element and a displacement device alternates the reading and writing positions.
In one aspect of the present invention, the displacement device wherein the displacement device comprising: a rotary needle installed below a read and write surface of the disc, a center of the rotary needle is installed with a fixed reflector, and selected positions at two sides thereof are installed with a movable reflector and a balance block; and a straight movement device for controlling the reflector and the balance block to move oppositely along a straight path on the rotary needle so as to control the alternation of the reading optic path.
In one aspect of the present invention, in data reading and writing, the disc and laser head are retained still. By the rotation of the rotary needle and the reciprocal straight path movement of the movable reflector and the balance block, the data at any position can be read and written. The beam from the laser head is transferred to the read and written surface through the fixing reflector and the movable reflector. The beam reflected from the disc reflecting layer returns to the laser head through the original path.
In one aspect of the present invention, the rotary driving device of the present invention has a small inertia, and thus a small power motor may serve the object. Similarly, the movable reflector, convex lens, and balance block are light and a small power servomotor can be used. Consequently, the power is saved greatly and defects in thermal power, vibration and noise can be avoided.